Many people around the world are getting this call right now: balance due, payment time, credit revoked. It's that kind of an economy. Even though we're on a slight upswing (unless you're in Greece, sorry Alliterative Allomorph), it takes a while for the ups to catch up to the downs--especially on the personal level. Plenty of people are stretched to the max--credit cards, second mortgages, car loans, etc., etc.
At some point, all of that lending and borrowing comes back to bite. At some point, the balance is due.
The same can be said for writing. Every character puts a certain amount of energy and effort into solving a problem, a certain amount of their life into the force behind building to the climax. And at some point in your book, they are owed, they want payment. They have to get something back to keep them going. That something might be your finale, or it might just be a dangling carrot.
Have you reached a point where your characters must get something more to keep going? Are they so involved in the plot that it doesn't seem believable? How do you balance their "normal" lives with where you want them to be?